Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Effect of Increasing Temperature and Precipitation on Water Use Efficiency of Desert Grassland Plants

Auteur : 王新雅

Grade : Master 2022

Université : Inner Mongolia Agricultural University

Résumé
Under the global climate change,the occurrence of grassland drought,extreme drought,or precipitation events always affects the development of grassland ecosystems,and water is an essential factor in the productivity of desert grassland ecosystems.In-depth insight into the effects of increasing temperature and precipitation on water use efficiency（WUE）of desert grassland plants can help understand grassland ecosystems desertification mechanisms from the perspective of water metabolism at the individual and community levels of plants.In this thesis,five different photosynthetic types of plants in the Stipa breviflora desert grassland of Siziwangqi,Inner Mongolia,were used to study the growth and water physiology of plants under different treatments in response to increasing temperature and precipitation by using a simulated temperature increase（OTC）method and a homemade rainfall interception device.The plant growth and water physiological responses to increasing temperature and precipitation under different treatments were investigated by measuring and analyzing the morphological characteristics,photosynthetic characteristics,water use efficiency,and stable carbon isotope characteristics of plant leaves.The main findings are as follows.（1）Increasing temperature and precipitation and their interactions significantly affected the height,cover,density,and relative biomass of C3 and C4 plants with changes in the growing period,reaching a maximum under the treatment of increasing temperature by 2°C and increasing precipitation by 50%,and plants adapted to the environment of increasing temperature and precipitation by growing height in the early and late growth periods.（2）The net photosynthetic rate（Pn）,stomatal conductance（Gs）,and transpiration rate（Tr）of plants increased significantly under increasing temperature,and the net photosynthetic rate（Pn）rose more than the transpiration rate（Tr）,but the intercellular carbon dioxide（Ci）did not change significantly ;when increasing precipitation by 50%,the Pn,Gs,Ci,and Tr of plants increased,but the water use efficiency of C4 was greater than that of C3.（3）The transient water use efficiency of Stipa breviflora was greatest in August,that of Artemisia frigida and Allium polyrhizum in July,and that of Cleistogenes songorica and Kochia prostrate in September,indicating that the transient water use efficiencies of different photosynthetic plants differed at different times.（4）Theδ13C values of C3 dominant plants of the three desert grasslands from light to heavy showed that short-flowered needlegrass had the highestδ13C values,the highest long-term water use efficiency,and theδ13C values of C4 dominant plants of the two desert grasslands were:Cleistogenes songorica＞Kochia prostrate,Cleistogenes songorica had the highest long-term water use efficiency,and the treatments of T,W and T*W had significant effects on theδ13C values of the plants（p＜0.05）

Mots clés : Desert grassland ;Water use efficiency ;Photosynthetic properties ;Stable carbon isotopes ;

Présentation (CNKI)